A conventional socket S, adapted for coupling a nut or bolt into a lower hole of the socket for rotatably fastening or unfastening the nut or bolt, includes a sloping circular opening T inclinedly formed in a top portion of the socket and a square hole H formed in the upper portion of the socket for coupling a driving (or coupling) shaft C into the square hole H as downwardly slid through the sloping circular opening T.
However, the right-angled corners C1 of the driving (or coupling) shaft C may be quadrilaterally retained on the sloping surfaces of the circular opening T as dotted line shown in FIG. 9. The user or operator must further twist or rotate the driving shaft C about the axis 10 either anti-clockwise R or clockwise R1 until matching the right-angled corners C1 of the shaft C with the square hole H of the socket S in order for stably coupling the shaft C into the socket hole H, thereby causing operating inconvenience for the tool user.
A conventional socket S has its bottom portion 1B formed with a hexagonal hole Hb to be engaged with a hexagonal nut or bolt N as shown in FIG. 10. When the apex corners X of the nut or bolt have been worn as curved corners, the worn nut or bolt may be slipped or slid when rotating the socket for driving the nut or bolt, thereby influencing a smooth engagement between the socket and the nut (or bolt) or delaying the driving operation for fastening the nut (or bolt).
The present inventor has found the drawbacks of the conventional socket and invented the present socket for quickly coupling driving tools, nuts or bolts.